The electronic structure of the s-indacenyl dianion. Structural assessment by nuclear magnetic resonance spectroscopy and molecular orbital calculations

Abstract

The ¹H and ¹³C n.m.r. chemical shifts of s-indacenyldilithium are reported and the results are compared with the charge pattern given by CNDO and ab initio MO calculations. Comparisons are also made with the corresponding data for the indenyl-lithium anion. Our observations are consistent with a delocalized, 14-π electron structure where most of the excess charge is located at the C-1, -3, and -4 positions.